|Publication number||US5442280 A|
|Application number||US 08/114,246|
|Publication date||Aug 15, 1995|
|Filing date||Sep 1, 1993|
|Priority date||Sep 10, 1992|
|Also published as||DE69318088D1, DE69318088T2, EP0587491A1, EP0587491B1, US5461309|
|Publication number||08114246, 114246, US 5442280 A, US 5442280A, US-A-5442280, US5442280 A, US5442280A|
|Original Assignee||Gec Alstom T & D Sa|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Non-Patent Citations (3), Referenced by (77), Classifications (12), Legal Events (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
R0 =r0 (αr -αs -αR)/αs
U=j S0 ωI R0 /(R0 +r0)
1. Field of the Invention
The present invention concerns the use of a Rogowski coil as described in U.S. patent application Ser. No. 08/067,628 filed 28 May 1993.
2. Description of the Prior Art
A coil of this kind comprises at least one printed circuit plate provided with a circular cutout, the coil being implemented by rectilinear metal deposits on each of the two faces of the plate and extending along radii such that geometrical projections thereof intersect at the center of said cutout, electrical connections between the radii on one face and those on the opposite face being implemented by plated-through holes that pass through the thickness of the plate.
A coil of this kind has perfect axial symmetry. The winding constituted by the radii and the holes comprises an outward leg and a return leg around the circular cutout with an input and an output on the same side on the plate separated by a distance of a few tenths of a millimeter. A coil of this kind is also relatively insensitive to temperature variations because the material supporting the winding is epoxy resin.
A first object of the invention is a simple way of using a coil of this kind to produce a current measuring device that is substantially insensitive to temperature variations.
Another object of the invention is to provide a temperature measuring device using a Rogowski coil of this kind.
Current is usually measured by means of a Rogowski coil by loading the coil with a high value resistor, measuring the voltage across this resistor and integrating this voltage. The invention utilizes this method, employing a particular value of the load resistor which renders the measurement substantially independent of temperature.
The temperature is measured by using the Rogowski coil winding as one arm of a Wheatstone bridge.
In one aspect, the invention consists in a device for measuring an electrical current in a conductor using a Rogowski coil through which said conductor passes, said Rogowski coil being of the type comprising at least one printed circuit plate provided with a circular cutout, the coil being implemented by metal deposits on each of the two faces of the plate and extending along radii such that geometrical projections thereof pass through the center of said cutout, electrical connections between the radii on one face and those on the opposite face being implemented by plated-through holes that pass through the thickness of the plate, the winding comprising an outward leg and a return leg around the cutout with an input and an output on the same face of the plate, separated by a distance of a few tenths of a millimeter, said device comprising a device for measuring the voltage U across a resistor R in series with said Rogowski coil, said resistor R having a value equal to
R0 =r0 (αr -αs -αR)/αs
R0 is the ohmic resistance of the resistor R at a reference temperature,
r0 is the ohmic resistance of the Rogowski coil at said reference temperature,
αR is the temperature coefficient of the conductive material of said Rogowski coil,
αs is the temperature coefficient of the sensitivity of the Rogowski coil,
αR is the temperature coefficient of the resistor R,
the current I to be measured being related to the voltage U by the equation:
U=j s0 ωI R0 /(R0 +r0)
s0 is the sensitivity of said Rogowski coil at said reference temperature,
j is the complex operator such that j2 =-1, and
ω is the angular frequency of the current to be measured.
In another aspect, the invention consists in a device for measuring temperature using a Rogowski coil of the type comprising at least one printed circuit plate provided with a circular cutout, the coil being implemented by metal deposits on each of the two faces of the plate and extending along radii such that geometrical projections thereof pass through the center of said cutout, electrical connections between the radii on one face and those on the opposite face being implemented by plated-through holes that pass through the thickness of the plate, the winding comprising an outward leg and a return leg around the cutout with an input and an output on the same face of the plate, separated by a distance of a few tenths of a millimeter, in which device said Rogowski coil of ohmic resistance r constitutes one of the branches of a Wheatstone bridge comprising three other resistors r2, r3 and r4, one diagonal of said bridge being connected to a voltage U, the voltage e measured across the other diagonal being related to the temperature θ by the equation:
A=((r.r40 (1+αθ)-r20.r30 (1+2αθ)),
B=((r+r20 (1+αθ)).((r30 (1+αθ).r40 (1+αθ)), and
r20, r30 and r40 are the respective ohmic resistance values of said resistors r2, r3 and r4, α denoting the common temperature coefficient of said resistors.
The invention is now described in detail with reference to the appended drawings.
FIG. 1 is a plan view of a Rogowski coil of the type used in the present invention.
FIG. 2 is a diagram showing how the aforementioned type Rogowski coil is wound.
FIG. 3 is a perspective view of a Rogowski coil with two active plates and one terminal plate.
FIG. 4 is a schematic of the Rogowski coil used as a voltage measuring device.
FIG. 5 is a schematic of the Rogowski coil used as a temperature measuring device.
FIG. 1 is a plan view of a Rogowski coil of the type used to implement the measuring devices in accordance with the invention.
It comprises a double-sided printed circuit plate, preferably of epoxy resin, advantageously reinforced with laminated glassfiber, and having a low coefficient of thermal expansion. As an alternative the plate may be made from ceramic or any like material having a very low coefficient of thermal expansion.
The plate is advantageously 1.6 mm thick.
The preferably square plate has a central hole 2 to receive the cable in which the current is to be measured.
The winding is constituted by deposits 3, etc of copper on each side of the plate; these deposits are rectilinear and radial, i.e. a line through them passes through the center O of the plate; as described later, the deposits on one face are connected to the deposits on the opposite face by plated-through holes 4 which pass through the plate.
The surface of the deposit is chemically stabilized by a deposit of gold of controlled thickness. This controls the internal resistance of the Rogowski coil.
The man skilled in the art knows how to substitute other appropriate deposits for the aforementioned gold and how to protect such deposits by appropriate means, for example by means of a protective varnish.
FIG. 1 shows the input 5 and the output 6 of the coil which are a few tenths of a millimeter apart to conform to the axial symmetry of the winding.
Holes 7 are used to fix the plate to other plates to construct a multiplate Rogowski coil.
FIG. 2 is a diagram showing how the winding is constituted. To produce perfect axial symmetry the winding is constituted by two windings in series, a first winding 10 wound clockwise and a second winding 20 wound anticlockwise. The figure is a diagrammatic plan view of part of the winding and uses the following conventions: the first winding 10 is shown in continuous thick line when the deposit is on the visible face of the plate and in dashed thick line when the deposit is on the opposite face; the second winding 20 is shown by a double line which is either continuous or dashed depending on whether the deposit is on the visible face or on the opposite face. To facilitate understanding of the diagram the two radii of the same turn are shown side-by-side but it must be understood that in reality the two radii are exactly aligned with each other on opposite faces of the plate. The arrow F1 shows the winding direction of the first winding. The arrow F2 shows the winding direction of the other winding. The windings 10 and 20 are connected in series at a point P.
FIG. 1 is drawn on a 1/1 scale. A plate this size may comprise in the order of 250 turns; it is possible to increase the sensitivity of the coil by using several cards of the type shown in FIG. 1. FIG. 3 shows a coil comprising three parallel cards 31, 41 and 51 fastened together by rods 60 passing through the holes 7; the cards 31 and 41 have triangular cutouts at one corner and of unequal size to facilitate connecting the coils by means of conductors (not shown) which pass through the plates perpendicularly to their plane.
In the FIG. 3 example the plate 51 does not have any cutout, is rectangular, and carries the electronic circuit for processing signals induced in the Rogowski coil, shown symbolically by the rectangle 61. The connections are therefore very short and do not induce any interference signals.
Note that the output connections are implemented as tracks (metal deposits) on the same side of the plate in order to minimize the influence of the magnetic field produced by the current to be measured.
If the Rogowski coil of the aforementioned type is loaded with a very high impedance (open circuit operation) the voltage across it is of the form:
e=s ω I=s2πfI
in which I is the current to be measured, ω is its angular frequency, f is its frequency and s is a coefficient of proportionality dependent on the coil and called the sensitivity of the coil.
The variation of the sensitivity s with temperature may be represented by the equation:
s=s0 (1+αs Δθ)
in which s0 is the sensitivity of the coil at a reference temperature, αs is the temperature coefficient, and Δθ is the temperature difference compared to the reference temperature.
For a coil of the aforementioned type the value of αs is around 60.10-6 /░C.
FIG. 4 is a schematic of the current measuring device of the invention. It comprises a Rogowski coil of the aforementioned type equivalent to an alternating current supply e in series with a resistor r (the resistor of the coil) and an inductor L (the self-inductance of the coil equal to Ns where N is the number of turns in the coil), loaded by a resistor R, and a voltage measuring device Us shunting the resistor.
The voltage Us is related to the current by the equation:
Us =j s ω I R/(R+r+jLω)
If αR is the temperature coefficient of the resistor R such that R=R0 (1+αR Δθ) and αr is the temperature coefficient of the resistor r (the resistance of the coil) such that r=r0 (1+αr Δθ):
Us =js0 ω I C/D
C=(1+αs Δθ)R0 (1+αR Δθ)
D=R0 (1+αR Δθ)+r0 (1+αr Δθ)+jNs0 ω(1+αs Δθ))
Neglecting αR (around 5.10-6 /░C.) in comparison with αs (around 60.10-6 /░C. as already mentioned), taking:
R0 =r0 (αr -αs -αR)/αs
and neglecting second order terms αr αs (Δθ)2 :
Us =(js0 ωI R0 /(R0 +r0)). 1/F
F=(1+jNs0 ω/(R0 +r0)). ((1+α0 Δθ)/(1+(αs +αR)Δθ)
Adopting the following approximations:
αR αs Δθ2 very much less than (αR +αs)Δθ, and
(αs +αR Δθ) very much less than 1:
Us =js0 ω(R0 /(r0 +R0)/(1+jNs0 ω(1-αR Δθ)/(R0 +r0))
In conclusion, the measured amplitude of the voltage is independent of temperature; choosing αR <5 ppm/░C. (NiCr resistance), the phase defined by the equation:
φs =arctan (Ns0 ω(1-αR Δθ)/(R0 +r0))
varies little with temperature.
FIG. 5 shows a temperature measuring device comprising a Wheatstone bridge one branch r of which is constituted by a Rogowski coil of the type described previously and the other branches r2, r3 and r4 of which are made from the same metal as the coil.
One diagonal of the bridge is connected to a voltage U, a DC voltage, for example. The other diagonal is connected to a voltage measuring device which measures a voltage e related to the temperature 0 by the equation:
A=((r.r40 (1+αθ)-r20.r30 (1+2αθ)),
B=((r+r20 (1+αθ)).((r30 (1+αθ).r40 (1+αθ)),
and r20, r30 and r40 are the respective resistances of the resistors r2, r3 and r4, α denoting their common temperature coefficient.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US4473810 *||Dec 15, 1982||Sep 25, 1984||La Telemecanique Electrique||Device for measuring the current which flows in a conductor|
|US4939449 *||Jun 29, 1989||Jul 3, 1990||Liaisons Electroniques-Mecaniques Lem Sa||Electric current sensing device of the magnetic field compensation type|
|US5055816 *||Jun 11, 1990||Oct 8, 1991||Motorola, Inc.||Method for fabricating an electronic device|
|CH665303A5 *||Title not available|
|DE721389C *||Jul 9, 1937||Jun 4, 1942||Siemens Ag||Anordnung zum Ausgleich der Temperaturfehler bei Messgleichrichterschaltungen fuer Hochfrequenzstroeme|
|1||*||French Search Report FR 9210801.|
|2||*||Japanese Patent Abstract 60 93325 dated May 25, 1985.|
|3||Japanese Patent Abstract 60-93325 dated May 25, 1985.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US5852395 *||Aug 12, 1997||Dec 22, 1998||Asea Brown Boveri Ag||Rogovski coil|
|US6094043 *||Apr 15, 1998||Jul 25, 2000||Square D Company||ARC detection sensor utilizing discrete inductors|
|US6094044 *||May 7, 1999||Jul 25, 2000||Airpax Corporation, Llc||AC current sensor having high accuracy and large bandwidth|
|US6313623||Feb 3, 2000||Nov 6, 2001||Mcgraw-Edison Company||High precision rogowski coil|
|US6330516||Mar 27, 2000||Dec 11, 2001||Power Distribution, Inc.||Branch circuit monitor|
|US6522256 *||May 15, 2001||Feb 18, 2003||Southern Electric Equipment||Hybrid current and voltage sensing system|
|US6624624 *||May 25, 2000||Sep 23, 2003||Arbeitsgemeinschaft Prof. Hugel Agph||Electrical current sensor|
|US6680608||Feb 27, 2002||Jan 20, 2004||Mcgraw-Edison Company||Measuring current through an electrical conductor|
|US6810069||Mar 24, 2003||Oct 26, 2004||Mcgraw-Edison Company||Electrical arc furnace protection system|
|US6825650 *||Jan 28, 2000||Nov 30, 2004||Suparules Limited||Current measuring probe and electrical energy meter for use therewith|
|US6940702||Mar 24, 2003||Sep 6, 2005||Mcgraw-Edison Company||Electrical protection system|
|US7180717||Mar 24, 2003||Feb 20, 2007||Cooper Technologies Company||Electrical network protection system|
|US7227441||Feb 4, 2005||Jun 5, 2007||Schweitzer Engineering Laboratories, Inc.||Precision Rogowski coil and method for manufacturing same|
|US7227442||Apr 1, 2005||Jun 5, 2007||Schweitzer Engineering Laboratories, Inc.||Precision printed circuit board based rogowski coil and method for manufacturing same|
|US7453267||Jan 17, 2006||Nov 18, 2008||Power Measurement Ltd.||Branch circuit monitor system|
|US7532000||Aug 3, 2006||May 12, 2009||The Boeing Company||Method and system for measurement of current flows in fastener arrays|
|US7545138||Jul 6, 2006||Jun 9, 2009||Schweitzer Engineering Laboratories, Inc.||Precision, temperature-compensated, shielded current measurement device|
|US7564233||Nov 6, 2006||Jul 21, 2009||Cooper Technologies Company||Shielded Rogowski coil assembly and methods|
|US7613578||Jun 7, 2007||Nov 3, 2009||Hagmann Mark J||Method for noninvasive determination of a distribution of electrical current and apparatus for the same|
|US7638999||Apr 7, 2006||Dec 29, 2009||Cooper Technologies Company||Protective relay device, system and methods for Rogowski coil sensors|
|US7738221||Dec 7, 2007||Jun 15, 2010||Cooper Technologies Company||Transformer inrush current detector|
|US7847543||May 28, 2008||Dec 7, 2010||Ladislav Grno||Precision flexible current sensor|
|US7902812||Jun 2, 2009||Mar 8, 2011||Cooper Technologies Company||Rogowski coil assembly and methods|
|US7902813||Sep 24, 2009||Mar 8, 2011||Cooper Technologies Company||Protective digital relay device|
|US8466756||Apr 17, 2008||Jun 18, 2013||Pulse Finland Oy||Methods and apparatus for matching an antenna|
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|US8786499||Sep 20, 2006||Jul 22, 2014||Pulse Finland Oy||Multiband antenna system and methods|
|US8829888||Sep 9, 2011||Sep 9, 2014||General Electric Company||Sensor devices and methods for use in sensing current through a conductor|
|US8866689||Jul 7, 2011||Oct 21, 2014||Pulse Finland Oy||Multi-band antenna and methods for long term evolution wireless system|
|US8872611||Aug 18, 2011||Oct 28, 2014||General Electric Company||Rogowski coil assemblies and methods for providing the same|
|US8912807||Sep 9, 2011||Dec 16, 2014||General Electric Company||Sensor devices and methods for use in sensing current through a conductor|
|US8928337||May 23, 2012||Jan 6, 2015||Schweitzer Engineering Laboratories, Inc.||Device for measuring electrical current and method of manufacturing the same|
|US8988296||Apr 4, 2012||Mar 24, 2015||Pulse Finland Oy||Compact polarized antenna and methods|
|US9075091||Sep 9, 2011||Jul 7, 2015||General Electric Company||Sensor devices and methods for use in sensing current through a conductor|
|US9081040||Jul 30, 2014||Jul 14, 2015||General Electric Company||Sensor devices and methods for use in sensing current through a conductor|
|US9151782||Nov 24, 2010||Oct 6, 2015||Pulse Electronics, Inc.||Current sensing devices and methods|
|US9183983||Oct 11, 2013||Nov 10, 2015||The Boeing Company||Modular equipment center integrated truss sensors|
|US9304149||Mar 12, 2013||Apr 5, 2016||Pulse Electronics, Inc.||Current sensing devices and methods|
|US9312059||Oct 18, 2013||Apr 12, 2016||Pulse Electronic, Inc.||Integrated connector modules for extending transformer bandwidth with mixed-mode coupling using a substrate inductive device|
|US9413162||Oct 11, 2013||Aug 9, 2016||The Boeing Company||Modular equipment center distributed independent protections|
|US9429595||Sep 9, 2011||Aug 30, 2016||Aclara Meters Llc||Sensor devices and methods for use in sensing current through a conductor|
|US9450291||Jul 25, 2011||Sep 20, 2016||Pulse Finland Oy||Multiband slot loop antenna apparatus and methods|
|US9461371||Nov 16, 2010||Oct 4, 2016||Pulse Finland Oy||MIMO antenna and methods|
|US9509054||Dec 1, 2014||Nov 29, 2016||Pulse Finland Oy||Compact polarized antenna and methods|
|US9511728||Oct 11, 2013||Dec 6, 2016||The Boeing Company||Modular equipment center distributed primary power architecture|
|US9531058||Dec 20, 2011||Dec 27, 2016||Pulse Finland Oy||Loosely-coupled radio antenna apparatus and methods|
|US9533636||Oct 11, 2013||Jan 3, 2017||The Boeing Company||Remote modular equipment center architecture|
|US9561760||Oct 11, 2013||Feb 7, 2017||The Boeing Company||Modular equipment center distributed equipment packaging truss|
|US9561761||Oct 11, 2013||Feb 7, 2017||The Boeing Company||Modular equipment center zonal standalone power system control architecture|
|US9561867||Oct 11, 2013||Feb 7, 2017||The Boeing Company||Modular equipment center lightning threat reduction architecture|
|US9590308||Dec 2, 2014||Mar 7, 2017||Pulse Electronics, Inc.||Reduced surface area antenna apparatus and mobile communications devices incorporating the same|
|US9634383||Jun 26, 2013||Apr 25, 2017||Pulse Finland Oy||Galvanically separated non-interacting antenna sector apparatus and methods|
|US20040008461 *||Mar 24, 2003||Jan 15, 2004||Kojovic Ljubomir A.||Electrical network protection system|
|US20040027748 *||Mar 24, 2003||Feb 12, 2004||Kojovic Ljubomir A.||Electrical protection system|
|US20060176140 *||Feb 4, 2005||Aug 10, 2006||James Kesler||Precision rogowski coil and method for manufacturing same|
|US20060220774 *||Apr 1, 2005||Oct 5, 2006||Veselin Skendzic||Precision printed circuit board based rogowski coil and method for manufacturing same|
|US20060238932 *||Jan 17, 2006||Oct 26, 2006||Westbrock William B Jr||Branch circuit monitor system|
|US20070236208 *||Apr 7, 2006||Oct 11, 2007||Cooper Technologies Company||Protective relay device, system and methods for Rogowski coil sensors|
|US20080007249 *||Jul 6, 2006||Jan 10, 2008||Wilkerson Donovan E||Precision, temperature-compensated, shielded current measurement device|
|US20080036448 *||Aug 3, 2006||Feb 14, 2008||Kovach Daniel J||Method and system for measurement of current flows in fastener arrays|
|US20080048646 *||Mar 2, 2007||Feb 28, 2008||Schweitzer Engineering Laboratories, Inc.||Precision, temperature-compensated, shielded current measurement device|
|US20080106253 *||Nov 6, 2006||May 8, 2008||Cooper Technologies Company||Shielded Rogowski coil assembly and methods|
|US20080275657 *||Jun 7, 2007||Nov 6, 2008||Hagmann Mark J||Method for noninvasive determination of a distribution of electrical current and apparatus for the same|
|US20080303511 *||May 28, 2008||Dec 11, 2008||Ladislav Grno||Precision flexible current sensor|
|US20090230948 *||Jun 2, 2009||Sep 17, 2009||Cooper Technologies Company||Rogowski Coil Assembly and Methods|
|US20100020457 *||Sep 24, 2009||Jan 28, 2010||Cooper Technologies Company||Protective Digital Relay Device|
|US20110025304 *||Sep 25, 2009||Feb 3, 2011||James Douglas Lint||Current sensing devices and methods|
|US20110025305 *||Jan 7, 2010||Feb 3, 2011||James Douglas Lint||Current sensing devices and methods|
|US20110148561 *||Nov 24, 2010||Jun 23, 2011||James Douglas Lint||Current sensing devices and methods|
|CN104034943A *||Jun 23, 2014||Sep 10, 2014||深圳市中鹏电子有限公司||PCB Rogowski coil current inductor based on differential wiring|
|CN104034943B *||Jun 23, 2014||May 4, 2016||深圳市中鹏电子有限公司||一种基于差分布线的pcb罗氏线圈电流感应器|
|DE19640981A1 *||Oct 4, 1996||Apr 16, 1998||Asea Brown Boveri||Rogowskispule|
|EP1615039A1 *||Jun 27, 2005||Jan 11, 2006||S.G.E. SocietÓ Generale di Elettronica S.r.l.||Voltage-measuring device for a high-voltage installation|
|WO1998048287A1 *||Apr 21, 1998||Oct 29, 1998||Liaisons Electroniques-Mecaniques Lem S.A.||Device with wide pass band for measuring electric current intensity in a conductor|
|WO2001057543A1 *||Feb 5, 2001||Aug 9, 2001||Mcgraw-Edison Company||High precision rogowski coil|
|WO2007061390A1||Nov 28, 2005||May 31, 2007||Ladislav Grno||Precision flexible current sensor|
|U.S. Classification||324/127, 374/E07.039, 324/117.00R|
|International Classification||G01K7/36, G01K7/22, G01K7/18, G01R15/18, G01R19/32|
|Cooperative Classification||G01R19/32, G01K7/36|
|European Classification||G01R19/32, G01K7/36|
|Sep 1, 1993||AS||Assignment|
Owner name: GEC ALSTHOM T&D SA, FRANCE
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